Fluorescent Materials and Thin Film Coatings for Temperature Sensing Applications

Accurate temperature monitoring in high-temperature mechanical systems is critical for ensuring operational safety, efficiency, and durability. These environments subject components to extreme thermal and mechanical stress, requiring robust and reliable temperature sensing methods. Traditional contact-based sensors, such as thermocouples and thermistors, often suffer from limited accuracy, signal drift, or physical degradation under harsh conditions. Non-contact techniques like pyrometry offer faster measurements but are constrained by emissivity dependence, line-of-sight integration, background emission, and environmental interference. To address these limitations, luminescent temperature sensors based on thermographic phosphors have emerged as a powerful alternative. These materials, typically composed of rare-earth-doped oxide ceramics, exhibit temperature-dependent luminescent properties that enable remote and accurate temperature sensing. When excited by a light source, the emitted light from these materials can be analyzed through either emission intensity ratios or fluorescence lifetime measurements to determine temperature without direct contact or emissivity correction. Integrating these phosphors into thin film structures is especially valuable for applications involving transparent windows or in scenarios where uniform coatings are needed. Among the various thin film fabrication techniques, e-beam deposition and ion assisted deposition (IAD) offers excellent control over film thickness, density, and dopant incorporation. IAD in particular combines physical vapor deposition with high energy ion bombardment to enhance film adhesion and microstructure while maintaining optical clarity. In this work, the multi-layer deposited films are annealed at high temperature for diffusion and phase formation. The resulting thin films assessed at room temperature and at temperatures above 1000oC exhibit strong photoluminescence under UV excitation. Advanced characterization techniques, including field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and grazing incidence X-ray diffraction (GIXRD), are employed to analyze the surface morphology and phase composition of the films. Furthermore, luminescent properties such as photoluminescence (PL) spectra and lifetime of these films are studied to observe the temperature dependence. By examining the temperature dependent behavior of luminescent properties, luminescent films can potentially be used as a method for measuring temperature on smooth surfaces or on transparent windows. This dissertation highlights the potential of Eu-doped yttrium oxide (yttria), Eu-doped ZnAl2O4 spinel, Dy-doped yttrium aluminum garnet (YAG), and Tb-doped gadolinium aluminum perovskite (GAP) coatings for enhancing the performance and durability of transparent windows in high-temperature applications. These rare-earth-doped thin film sensors present a promising solution for real-time, non-contact temperature monitoring in extreme environments, supporting the advancement of safer and more efficient high temperature systems and devices.

Name thesis:degree_name

Materials Science and Engineering, PhD

Grantor

Georgia Institute of Technology

Year dc:date.issued

2026

Author dc:creator

• Kim, Richard

Advisor dc:contributor.advisor

• Ratcliff, William C.

Committee members dc:contributor.committeemember

• Mazumdar, Ellen
• Kang, Zhitao
• Zhang, Yuelan
• Losego, Mark

Handle dc:identifier.uri

https://hdl.handle.net/1853/81697

OAI identifier oai:identifier

oai:repository.gatech.edu:1853/81697